1. Technical Field
The present disclosure relates to a method and an apparatus for detecting a photolithography processing error; more particularly, a method and an apparatus for detecting a photolithography processing error in advance of a photolithography process.
2. Discussion of Related Art
Generally, a semiconductor device is manufactured by a series of processes such as a process of forming a thin film, a diffusion process, an ion implantation process, a photolithography process and an etching process. For example, a thin film is formed on a substrate in the process of forming a thin film. Impurities are implanted into a surface of the substrate in the ion implantation process. The impurities are diffused in the substrate in the diffusion process. A photoresist layer formed on the thin film is exposed and developed in the photolithography process to form a photoresist pattern. The thin film is etched using the photoresist pattern as an etching mask in the etching process.
As a semiconductor device becomes more highly integrated, the dimensions of the photoresist pattern are reduced, and equipment capable of forming minute photoresist patterns is needed.
A method of forming a minute photoresist pattern is disclosed in U.S. Pat. No. 5,363,171. In the method, when a photoresist pattern is formed on a substrate using a photo mask and a photoresist layer, a reflectivity of the photoresist layer is measured in-situ. Korean Patent Laid Open Publication No. 2000-051492 discloses a reflectivity measurement member, which measures a reflectivity of a wafer. A controller controls an exposure time of the wafer according to the reflectivity of the wafer measured by the reflectivity measurement member. The exposure time varies in accordance with the reflectivity of the wafer to form a photoresist pattern having a desired critical dimension.
In forming a photoresist pattern, it is preferred that the pattern is formed on a substrate in the photolithography process. Generally, the photolithography process is performed using an optical characteristic of a photoresist layer. A portion of the photoresist layer exposed to light has different properties from another portion of the photoresist layer not exposed to light. Accordingly, when the photoresist layer is exposed to light, the photoresist layer can be partially removed to form a photoresist pattern. To block light from passing through the photoresist layer, an anti-reflective layer is typically formed beneath the photoresist layer. The photolithography process varies according to a material characteristic of an underlying layer. When the light partially passes through the anti-reflective layer, the photoresist pattern may not have a desired configuration. As a result, the underlying layer may not have a desired critical dimension.
The photolithography process is monitored by measuring the critical dimension of the underlying layer on the substrate using a scanning electron microscope (SEM) or by inspecting a surface of the substrate. Generally, SEMs have a high magnification and is used for accurately measuring the critical dimensions. However, it is timing consuming to scan the entire surface of the substrate using the SEM because many measurement points on the surface of the substrate are required.
If a defect generated in the photolithography process may be detected in a detection process performed after the photolithography process, repetition of the photolithography process can be avoided.